Combined therapy for nmdar antagonist-responsive neuropsychiatric disorders

ABSTRACT

Described herein are compositions, including an oral dosage regimen, for the treatment of NMDAR-related neuropsychiatric disorders such as depression and obsessive-compulsive disorder and that includes an NMDAR antagonist, such as D-cycloserine formulated to produce plasma levels in excess of 25 microgram/mL, combined with more recently developed antidepressants.

CROSS REFERENCE TO RELATED APPLICATIONS

Benefit is claimed to U.S. Provisional Patent Application No.62/510,801, filed May 25, 2017, and U.S. Provisional Patent ApplicationNo. 62/518,020, filed Jun. 12, 2017; the contents of both of which areincorporated by reference herein in their entirety.

FIELD

Provided herein is an oral dosage regimen for the treatment ofNMDAR-related neuropsychiatric disorders such as depression andobsessive compulsive disorder, wherein the treatment includes an NMDARantagonist, such as D-cycloserine formulated to produce plasma levels inexcess of 25 microgram/mL, combined with more recently developedantidepressants.

BACKGROUND

Major depression is a clinical syndrome that includes a persistent sadmood or loss of interest in activities, which persists for at least twoweeks in the absence of treatment. Symptoms of major depression aretypically measured using rating scales such as the Hamilton DepressionRating Scale (HAM-D) or the Beck Depression Inventory (BDI). In additionto including symptoms relevant to depressed mood, the HAM-D alsocontains symptoms sensitive to psychosis, including items for guilt,depersonalization/derealization and paranoia. Major depression may alsobe associated with symptoms of anxiety, which may be measured withrating scales such as the Hamilton Rating Scale for Anxiety (HAM-A).Depressive disorders are divided into major depression (MDD) and bipolardepression (BPD). Major depression may also occur with and withoutmelancholic features. In addition, depressive symptoms may occur in thecontext of anxiety disorders such as generalized anxiety disorder,dissociative disorders, personality disorders or adjustment disorderswith depressed mood (DSM-IV).

Other forms of depression include atypical depression, agitateddepression, depression with mixed emotional features, cyclothymia,dysthymia minor depression and adjustment disorder with depressed mood.Bipolar depression may be divided into Bipolar I and Bipolar II subtypesbased upon presence or absence of manic episodes. In bipolar disorder,depressive symptoms can occur in the context of either a depressiveepisode, or a mixed state in which symptoms of mania and depressionoccur simultaneously or in rapid sequence. Rapid cycling between maniaand depressive episodes may also occur in some individuals.

Risk for suicide is significantly increased in depressive disorders, butmay respond differentially to medication versus depressive symptoms as awhole. When suicide occurs, it is often accompanied by feelings ofworthlessness or inappropriate guilt, as well as recurrent thoughts ofdeath or suicidal ideation and guilt is an accepted proxy for suicide.While the risk of suicide increases in subjects with a depressivedisorder, medications used to date to typically treat depressivedisorders paradoxically increase suicidal tendencies.

Most current theories of depression focus on serotonergic and/ornoradrenergic brain systems. Current treatments for major depressionconsist primarily of older antidepressants, such as monoamine oxidaseinhibitors (MAOI) and tricyclic antidepressants (TCAs) (e.g. imipramine,amitryptiline, desipramine, clomipramine) that were first developed inthe 1960's, and newer agents such as tetracyclic antidepressants (TeCAs)(e.g., mianserin, mirtazapine), serotonin (SSRI) andserotonin/norephinephrine (SNRI) reuptake inhibitors (e.g., fluoxetine,fluvoxamine, paroxetine, citalopram, escitalopram, duloxetine,venlafaxine, dapoxetine, indalpine, milnacipran, levomilnacipran). MAOIsand TCAs are considered “broader spectrum” agents than SSRIs/SNRIs thatwere developed subsequently.

Glutamate is an alternative brain neurotransmitter that has been studiedto a limited degree in relationship to depression or other affectivedisorders. Glutamate binds to several receptor types includingN-methyl-D-aspartate type glutamate receptors (NMDAR). NMDAR containmultiple binding sites including an agonist site for glutamate and anallosteric modulatory site (aka glycineB receptor,strychnine-insensitive glycine receptor) sensitive to the endogenousbrain amino acids glycine and D-serine. Agonists at the glycine siteincrease NMDAR activation in response to glutamate while antagonistsdecrease NMDAR activation.

Functional agonists and antagonists at the glycine site can beidentified using well-validated electrophysiological assays such asmodulation of NMDAR-mediated responses to NMDAR glutamate-site agonists,or radio-receptor assays, such as modulation of binding to the NMDARPCP-receptor channel binding site. Glycine site agonists and antagonistscan also be distinguished based upon both electrophysiology and receptorbinding from compounds such as phencyclidine (PCP) or ketamine that bindto the channel site (aka PCP receptor, uncompetitive antagonist site) ofthe NMDAR. Effective agonists and antagonists may be identified, forexample, as compounds with <100 nM affinity for their targetand >10-fold selectivity vs. other relevant targets. Partial agonistsare defined as compounds that have reduced efficacy for inducingconformational change in receptors (typically 40-80%) relative to fullagonists, and which may induce agonist effects at low dose butantagonist effects at high dose.

Despite the wide range of pharmacological options, current treatmentapproaches for depression have severe limitations. Only 60-65% ofpatients respond to the initial regimen and among those responding, lessthan half either reach remission or become symptom-free. Individuals notresponding to a first course of antidepressant treatment are oftenswitched to a different drug, with results that are generally modest andincremental.

Within major depression, treatment-refractory depression refers to aform of depression that responds poorly to currently availabletreatments (e.g., see nimh.nih.gov/trials/practical/stard/index.shtmlJune 2011) and which may have different underlying etiopathologicalmechanisms compared with other forms of depression. Combinations ofantidepressants have not been shown to be superior to monotherapy forrefractory depression and typically increase risk of side effects andare not recommended. Thus a continuing need exists for effectivetreatments for major depression and other disorders related to excessNMDAR activation.

SUMMARY

Newer SNRIs and atypical antidepressants differ from traditionalmedications in that they have higher specificity for targets other thanthe serotonin transporter, and thus are relatively more similar to TCAsin having balanced modulation of serotonergic and noradrenergicsymptoms. In general, the newer agents have efficacy similar to those ofmore traditional SSRIs and SNRIs, but differential side effect profiles(Wagner et al., Journal of Affective Disorders 228:1-12, 2018). Theirrelative interaction with ketamine or other NMDAR-based antidepressionagents has not been previously studied. It has now been observedunexpectedly that newer SNRIs/atypical antipsychotics have preferentialbeneficial activities in combination with a D-cycloserine-doseassociated with plasma levels >25 microgram/mL, and thus show unexpectedutility of combinations involving high dose D-cycloserine and neweranti-depressant agents.

Accordingly, described herein are formulations containing a NMDARantagonistcombined with an anti-depressant that is drawn from a listthat includes levomilnacipran, milnacipran, vilazadone, vortioxetine,S-mirtazapine and R-mirtazapine.

Uses of the described compositions in methods for treatment ofdepression, OCD, and anxiety disorders, and for preparation of amedicament for use in such treatments are also described.

The foregoing and other objects, features, and advantages will becomemore apparent from the following detailed description, which proceedswith reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the effect of indicated mg/kg (mpk) doses ofD-cycloserine (DCS) on immobility time in the forced swim test (FST)following oral (PO) administration relative to control (ctl) or activecomparator (sertraline). * p<0.05 vs. Ctl; ***p<0.001 vs. Ctl

FIG. 2 is a graph showing the effect of DCS in combination withindicated antidepression agents. As indicted, *p<0.05, **p<0.01,***p<0.001 No DCS vs. 300 mg/kg. #p<0.05 vs. DCS 300 mg/kg alone.

FIG. 3 shows the synergistic effects of DCS and mirtazapine on marbleburying ***p<0.001 vs. Vehicle. #p<0.05 mirtazapine+DCS 300 mg/kg vs.mirtazapine alone. 10 mice were treated with either Vehicle (control),Paroxetine (5 mg/kg), Mirtazapine (5.5 mg/kg), D-cycloserine (30 mg/kg),D-cycloserine (300 mg/kg) or D-cycloserine (300 mg/kg)+(Mirtazapine 5.5mg/kg) which was administered by IP 30 minutes prior to test. Distancetraveled during the test was captured by cameras and quantified usingVideo Tracker Software (ViewPoint Life Sciences Software, France). Atthe end of the test mice were removed from the cages and the number ofunburied marbles was counted. A marble was considered buried if it wascovered at least two thirds with bedding. An effect was consideredsignificant if p<0.05.

FIG. 4 shows the relative effects of R- and S-isomers of mirtazapine onmarble burying, showing greater effects of R- vs S-isomer. ***p<0.001vs. racemic mirtazapine. 10 mice were treated with either Vehicle(control), Paroxetine (5 mg/kg), S-Mirtazapine (1, 2.5, 5.0, and 10mg/kg), R-Mirtazapine (1, 2.5, 5.0, and 10 mg/kg), R-Mirtazapine (2.5mg/kg)+D-cycloserine (300 mg/kg) which was administered by IP 30 minutesprior to test. Distance traveled during the test was captured by camerasand quantified using Video Tracker Software (ViewPoint Life SciencesSoftware, France). At the end of the test mice were removed from thecages and the number of unburied marbles was counted. A marble wasconsidered buried if it was covered at least two thirds with bedding. Aneffect was considered significant if p<0.05.

DETAILED DESCRIPTION I. Terms

Unless otherwise explained, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this disclosure belongs. The singular terms“a,” “an,” and “the” include plural referents unless context clearlyindicates otherwise. Similarly, the word “or” is intended to include“and” unless the context clearly indicates otherwise. It is further tobe understood that all base sizes or amino acid sizes, and all molecularweight or molecular mass values, given for nucleic acids or polypeptidesare approximate, and are provided for description. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of this disclosure, suitable methods andmaterials are described below. The term “comprises” means “includes.”“Consisting essentially of” indicates a composition, method, or processthat includes only those listed features as the active or essentialelements, but can include non-active elements in addition. Theabbreviation, “e.g.” is derived from the Latin exempli gratia, and isused herein to indicate a non-limiting example. Thus, the abbreviation“e.g.” is synonymous with the term “for example.”

In case of conflict, the present specification, including explanationsof terms, will control. In addition, all the materials, methods, andexamples are illustrative and not intended to be limiting.

Administration: The introduction of a composition into a subject by achosen route. Administration of an active compound or composition can beby any route known to one of skill in the art. Administration can belocal or systemic. Systemic administration includes any route ofadministration designed to distribute an active compound or compositionwidely throughout the body via the circulatory system. Thus, systemicadministration includes, but is not limited to oral, intra-arterial andintravenous administration.

Analog, derivative or mimetic: An analog is a molecule that differs inchemical structure from a parent compound, for example a homolog(differing by an increment in the chemical structure, such as adifference in the length of an alkyl chain), a molecular fragment, astructure that differs by one or more functional groups, a change inionization. Structural analogs are often found using quantitativestructure activity relationships (QSAR), with techniques such as thosedisclosed in Remington (The Science and Practice of Pharmacology, 19thEdition (1995), chapter 28). A derivative is a biologically activemolecule derived from the base structure. A mimetic is a molecule thatmimics the activity of another molecule, such as a biologically activemolecule. Biologically active molecules can include chemical structuresthat mimic the biological activities of a compound. It is acknowledgedthat these terms may overlap in some circumstances. It is to beunderstood that the active agents described herein can be substituted byfunctionally equivalent derivatives and analogs to similar effect.

Antagonist: A molecule or compound that tends to nullify the action ofanother, or in some instances that blocks the ability of a givenchemical to bind to its receptor or other interacting molecule,preventing a biological response.

Effective amount or a therapeutically effective amount: indicates anontoxic but sufficient amount of the same to provide the desiredeffect. In a combination therapy of the present invention, an “effectiveamount” of one component of the combination is the amount of thatcompound that is effective to provide the desired effect when used incombination with the other components of the combination. The amountthat is “effective” will vary from subject to subject, depending on theage and general condition of the individual, the particular active agentor agents, and the like. Thus, it is not always possible to specify anexact “effective amount.” However, an appropriate “effective” amount inany individual case may be determined by one of ordinary skill in theart using routine experimentation.

D-cycloserine (DCS): refers to the chemical D-cycloserine (CA IndexName: 3-Isoxazolidinone, 4-amino-, (4R)-(9CI); CAS Registry No.68-41-7), or pharmaceutically acceptable salts thereof. DCS is an FDA(United States Food and Drug Administration)-approved drug for treatmentof tuberculosis, and is sold by Eli Lilly and Company under the tradename Seromycin®. DCS is a structural analog of D-alanine, and is abroad-spectrum antibiotic produced by some strains of Streptomycesorchidaceus and S. garphalus. DCS is also described herein as“cycloserine.”

Parenteral: Administered outside of the intestine, for example, not viathe alimentary tract. Generally, parenteral formulations are those thatwill be administered through any possible mode except ingestion. Thisterm especially refers to injections, whether administeredintravenously, intrathecally, intramuscularly, intraperitoneally, orsubcutaneously, and various surface applications including intranasal,intradermal, and topical application, for instance.

Pharmaceutically acceptable carriers: The pharmaceutically acceptablecarriers useful in this disclosure are conventional. Remington'sPharmaceutical Sciences, by E. W. Martin, Mack Publishing Co., Easton,Pa., 15th Edition (1975), describes compositions and formulationssuitable for pharmaceutical delivery of the compounds herein disclosed.In general, the nature of the carrier will depend on the particular modeof administration being employed. For instance, parenteral formulationsusually comprise injectable fluids that include pharmaceutically andphysiologically acceptable fluids such as water, physiological saline,balanced salt solutions, aqueous dextrose, glycerol or the like as avehicle. For solid compositions (for example, powder, pill, tablet, orcapsule forms), conventional non-toxic solid carriers can include, forexample, pharmaceutical grades of mannitol, lactose, starch, ormagnesium stearate. In addition to biologically-neutral carriers,pharmaceutical compositions to be administered can contain minor amountsof non-toxic auxiliary substances, such as wetting or emulsifyingagents, preservatives, and pH buffering agents and the like, for examplesodium acetate or sorbitan monolaurate.

Pharmaceutical agent: A chemical compound or composition capable ofinducing a desired therapeutic or prophylactic effect when properlyadministered to a subject or a cell.

Subject: Living multi-cellular organisms, including vertebrateorganisms, a category that includes both human and non-human mammals.The human subjects described herein are also referred to as “patients.”

Subject susceptible to a disease or condition: A subject capable of,prone to, or predisposed to developing a disease or condition. It isunderstood that a subject already having or showing symptoms of adisease or condition is considered “susceptible” since they have alreadydeveloped it. For example, it is appreciated that patients sufferingfrom depression are susceptible to suicidality.

Treating and Treatment: refer to reduction in severity and/or frequencyof symptoms, elimination of symptoms and/or their underlying cause,prevention of the occurrence of symptoms and/or their underlying cause,and improvement or remediation of damage. Thus, for example, “treating”a patient involves prevention of a particular disorder or adversephysiological event in a susceptible individual as well as treatment ofa clinically symptomatic individual.

II. Overview of Several Embodiments

Described herein are compositions for use in treatment of a NMDAreceptor neuropsychiatric disorder in a human subject, which includes atherapeutic effective amount of a first agent that is a NMDA receptorantagonist; and a second agent that is an anti-depressant selected fromlevomilnacipran, milnacipran, vilazadone, vortioxetine, S-mirtazapineand R-mirtazapine, and wherein the NMDA receptor neuropsychiatricdisorder is selected from depression, obsessive compulsive disorder, andanxiety disorders.

In particular embodiments, the first agent is D-cycloserine provided ata net antagonistic dose, such as a dose of ≥500 mg/day to ≤1000 mg/dayand is formulated to produce an average plasma level in the subject ofgreater than 25 μg/mL, and more particularly a dose of 7.5-12.5mg/kg/day.

In other particular embodiments, the first agent is selected fromketamine, GlyX-13, NRX-1074, NYX-2925, AGN-241751 and Gavestinel.

In some embodiments, the described composition is used in treatments ofdepression that is major depression, major depressive disorder,atypical, agitated, melancholic depression or dysthymic disorder. Inother embodiments, the depression is bipolar disorder, such as bipolartype I or bipolar type 2 depressive disorder or is associated withdepressive or mixed episodes associated with bipolar depression.

In some embodiments, the described composition reduces symptoms ofdepression, reduces suicide incidence or treats suicide ideation in thesubject. In other embodiments, the disorder is associated withsuicidality.

Also provided herein is a composition that includes a first agent thatis a NMDA receptor antagonist; and a second agent that is anantidepressant selected from levomilnacipran, milnacipran, vilazadone,vortioxetine, S-mirtazapine and R-mirtazapine.

In particular embodiments of the described composition the first agentis D-cycloserine provided at a net antagonistic dose, such as ≥500mg/day to ≤1000 mg/day and to produce an average plasma level in asubject of greater than 25 mg/mL, and such as 7.5-12.5 mg/kg/day.

In other particular embodiments of the described composition, the firstagent is selected from ketamine, GlyX-13, AGN-241751 and Gavestinel.

In still further embodiments, the described composition is formulated ina sustained release formulation.

Methods of treatment of a NMDA receptor-responsive neuropsychiatricdisorder selected from depression, obsessive compulsive disorder, andanxiety disorders, by administering to a subject a therapeuticallyeffective amount of any of the above described compositions are alsodescribed.

Additionally provided are uses of the described compositions in thepreparation of a medicament for treatment of the described conditions.

III. Methods for Treatment of Depression, OCD, and Anxiety Disorders

Demonstrated herein is the finding that antagonistic D-cycloserineplasma levels are associated with rodent anti-depressive effects. Alsoprovided is the first demonstration of D-cycloserine augmentation oflocomotor hyperactivity, and the first demonstration that differentclasses of antidepressant are differentially capable of modulatinglocomotor hyperactivity in combination with D-cycloserine provided at anet antagonist dosage, suggesting differential clinical effectiveness.These findings permit development of unexpected dosing strategies forD-cycloserine for the treatment of human neuropsychiatric illness, andsuggest unexpected beneficial combinatorial effects of D-cycloserinewith specific types of anti-depressant medication, and particularly,more recently developed antidepressant agents. In view of these andother described observations, provided herein are compositions andmethods for treatment of neuropsychiatric conditions associated withexcessive NMDR neurotransmission, and particularly depression,obsessive-compulsive disorder, and anxiety disorders.

In one embodiment, described composition includes two activeingredients, wherein the first of the two active ingredients is an NMDARantagonist agent, such as D-cycloserine formulated to produce sustainedplasma D-cycloserine levels of >25 microgram/mL and wherein the secondof the two active ingredients is an antidepressant, which in certainembodiments can be selected from levomilnacipran, milnacipran,vilazadone, vortioxetine, S-mirtazapine and R-mirtazapine.

The compositions described herein are composed of an NMDAR antagonistcompound. NMDARs are a type of neuronal receptor for the brainneurotransmitter glutamate. NMDARs participate in a range of brainfunctions including sensory processing, cognition, and emotionregulation. NMDARs are comprised of multiple subunits termed GluN1,GluN2 and GluN3 (formerly NR1, NR2, NR3). Multiple forms of GluN1, GluN2and GluN3 exist. An NMDAR may consist of various combinations of GluN1,GluN2 and GluN3 subunits in various amounts. Agonists and antagonistsmay affect all NMDARs equivalently, or may be selective for an NMDARcontaining specific subunit types. The methods described herein includeuse of NMDAR antagonists.

Recently, the non-competitive NMDAR antagonist ketamine has also beenshown to have antidepressant effects in humans when tested inindividuals with treatment-resistant depression. The compound showssimilar effects in both unipolar and bipolar depression. Othernon-competitive NMDAR antagonists such as MK-801 also showanti-depressant effects in animal models. However, antidepressanteffects induced by ketamine are associated with exacerbation ofpsychosis, which greatly reduces their utility in clinical situations.

NMDARs contain binding sites for the neurotransmitter glutamate and forthe endogenous modulatory amino acids glycine and D-serine. NMDARs alsoare sensitive to the redox state of the surrounding tissue via a redoxsite/polyamine binding site. Agents that bind to these sites and reduceNMDAR activity are termed competitive inhibitors.

The NMDAR glutamate binding site selectively binds the syntheticglutamate derivative N-methyl-D-aspartate with high affinity. This siteis alternately referred to as the glutamate recognition site or the NMDArecognition site of the NMDAR.

The NMDAR glycine/D-serine binding site has been referred to as theglycine modulatory site, the allosteric modulatory site or the glycine-Breceptor.

NMDARs form an ion channel that is blocked by several drugs of abuse,such as phencyclidine (PCP), ketamine, or dizocilpine (MK-801). Thesecompounds bind to a site that has been termed the PCP receptor. Agentsthat block the NMDAR-associated ion channel are collectively termednon-competitive NMDAR antagonists, or NMDAR channel blockers. Blockadeof NMDARs by channel blockers leads to a clinical psychotic state thatclosely resembles schizophrenia.

In the described methods, NMDARs may also be inhibited by antagoniststhat bind to the glutamate recognition sites, the glycine recognitionsite, or the polyamine binding site. Historically, high affinity NMDARantagonists have been used in multiple clinical settings.

Selfotel (CGS19755) is an example of an antagonist that binds to theglutamate recognition site. Several such compounds were developed forCNS indications such as stroke or epilepsy. When used at dosessufficient to significantly inhibit NMDAR, these compounds, like channelblockers, lead to clinical psychotomimetic symptoms.

Additional compounds that function as antagonists of the glutamaterecognition site include aptiganel (Cerestat, CNS-1102) and relatedcompounds as described in Reddy et al., J Med Chem 37:260-7. 1994).Additional compounds that function as antagonists of the glutamaterecognition site include alpha.-amino-carboxylic acid and phosphonicacid functionalities separated by a variety of spacer units. Anunembellished example is 2-amino-5-phosphonovaleric acid (AP5) (Watkins,J. C.; Evans, R. H., Annu. Rev. Pharmacol. Toxicol. 1981, 21, 165),which contains a saturated carbon chain. More complex examples, whichcontain elements enhancing structural rigidity and therefore potency,include CPP, cis-4-(phosphonomethyl)-2-piperidinecarboxylic acid(CGS-19755) (Lehman, J. et al., J. Pharmacol. Exp. Ther. 1988, 246, 65),and (E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid (CGP-37849)(Schmutz, M. et al., Abs. Soc. Neurosci. 1988, 14, 864). See U.S. Pat.No. 7,345,032, issued Mar. 18, 2008 and U.S. Pat. No. 5,168,103,incorporated herein by reference in its entirety.

In the described methods, NMDARs may also be inhibited by antagoniststhat bind to the glycine recognition site. In a particular embodiment,such inhibition is by D-cycloserine, administered at an antagonistproducing dosage.

D-cycloserine, also referred to herein as “cycloserine”, is a compoundcurrently approved for treatment of tuberculosis (TB). Psychotropiceffects of cycloserine were noted in the late 1950's in patients beingtreated for TB. In an initial report, effects of cycloserine were notedon symptoms such as anorexia, asthenia and insominia. However, no formalpsychiatric diagnoses were made. Furthermore, cycloserine wasrecommended primarily for treatments of tension and insomnia, as opposedto depression.

Because of its ability to bind to NMDAR and because of theories linkingNMDAR to schizophrenia, D-cycloserine has been studied in treatmentresistant schizophrenia. At low doses, D-cycloserine has been found toproduce beneficial effects in some but not all studies, and mayexacerbate symptoms in individuals receiving clozapine. Furthermore, athigher doses (≥250 mg), however, D-cycloserine exacerbates psychosis andso according to package label insert is contra-indicated inschizophrenia, depression and anxiety disorders. Research withD-cycloserine in preclinical models has also not suggested itsusefulness at high dose in treatment of depression. Partial agonists ofNMDAR, in particular 1-aminocyclopropanecarboxylic acid (ACPC) have beenreported to have efficacy in animal models, but have not yet been testedin human studies. Furthermore, effects were only observed at the lowestdose tested, arguing away from high dose treatment in humans. In animaldepression models, tolerance over weeks has also been observed, arguingagainst sustained long term use.

For example, D-cycloserine reported for use at a dose of 250 mg/day wasfound to be without significant effect on symptoms of major depressionand moreover, commonly available prescribing information states thatD-cycloserine use is contraindicated in individuals with a history ofepilepsy, depression, severe anxiety, or psychosis (Lilly. Seromycin(cycloserine) capsules prescribing information. Indianapolis, Ind.; 2005Apr. 28).

D-cycloserine produces primarily agonist effects at doses up toapproximately 100 mg, and primarily antagonist effects at doses above500 mg, with intermediate effects at intermediate doses. Plasmaconcentrations associated with primarily agonist effects are primarily<10 μg/mL. Plasma concentrations associated with antagonist effectsare >25 μg/ml. Increased liability for toxicity is observed at plasmalevels >35 μg/mL.

D-cycloserine is typically administered for the treatment oftuberculosis at doses of 250-1000 mg. Thus, typical doses are 250 mg,500 mg, 750 mg or 1000 mg. Intermediate doses, such as 550, 600, 650,700, 800, 850 or 900 mg are also possible. In particular embodiments ofthe described compositions and methods, D-cycloserine is administered toa subject at a dose of greater than 500 mg/day to less than or equal to1000 mg/day, including but not limited to the above intermediate doses.Effective doses of D-cycloserine for the intended use in humans requiresustained plasma levels exceed >25 ug/ml, which in particularembodiments is provided by a dosage of greater than or equal to 10 mg/kgin an adult subject. Achievement of these levels requires human doses inexcess of 500 mg/day, which in an average adult will be about 700 mg/dayor greater. Human dosing of D-cycloserine to produce net antagonisteffects can be understood from human pharmacokinetics studies. Inparticular embodiments, DCS is given at a dose between 10 mg/kg/day-25mg/kg/day. In other particular embodiments, it is also understood thatdepending on the metabolism of the subject, the DCS can be given at adose of 7.5-12.5 mg/kg/day.

Pharmacokinetics (PK) of D-cycloserine in humans after a dose of 500 mghave been previously studied. Critical parameters include maximum (peak)concentration achieved (Cmax), time to maximum concentration (Tmax) andarea under the curve (AUC) during the dosing interval.

For example, Zhu et al. (Zhu M, Nix D E, Adam R D, Childs J M, PeloquinC A. Pharmacokinetics of cycloserine under fasting conditions and withhigh-fat meal, orange juice, and antacids. Pharmacotherapy. 2001;21(8):891-7) showed median Cmax values of 14.8 microgram/mL underfasting conditions, with a range of 12.1-30.6 microgram/mL. Median AUClevels over 24 hr were 214 microgram-hr/mL with a range of 163-352,corresponding to median sustained plasma levels of 8.9 microgram/mL witha range of 6.8-14.7 microgram/mL.

Park et al., (Park S I, Oh J, Jang K, Yoon J, Moon S J, Park J S, Lee JH, Song J, Jang I J, Yu K S, Chung J Y. Pharmacokinetics of Second-LineAntituberculosis Drugs after Multiple Administrations in HealthyVolunteers. Antimicrob Agents Chemother. 2015; 59(8):4429-35.) evaluatedpharmacokinetics of 250 mg PO D-cycloserine given every 12 hrs, andobserved mean Cmax values of 24.9 microgram/mL and a mean AUC over 12hrs of 242.3 mg-h/L, corresponding to a mean plasma level of 20. 2microgram/mL.

Hung et al., 2014 (Hung W Y, Yu M C, Chiang Y C, Chang J H, Chiang C Y,Chang C C, Chuang H C, Bai K J. Serum concentrations of cycloserine andoutcome of multidrug-resistant tuberculosis in Northern Taiwan. Int JTuberc Lung Dis. 2014; 18(5):601-6) evaluated PK levels during clinicaltreatment with DCS. Mean dose across subjects was 8.8 mg/kg, with themajority of subjects (n=27) receiving 500 mg/day DCS, and a minorityeither 750 mg/d (n=4) or 250 mg/d (n=2). DCS concentrations at 2 and 6hr after dosing were 19.7 and 18.1 microgram/mL.

Thus, a consistent finding of human PK studies is that sustained plasmadoses following 500 mg administration of D-cycloserine are consistentlybelow 25 microgram/mL. As described herein, the antidepressant effectsof D-cycloserine are observed at dosages above 25 microgram/mL.Accordingly, the daily dose for producing such plasma levels willnecessarily be above 500 mg/day, as described herein. Such doses includeamounts greater than 10 mg/kg/day, such as 10, 12, 14, 16, and 18mg/kg/day.

Felbamate is another example of a compound that may act via the glycinebinding site, and which can be used in the described methods. Whenadministered to humans, felbamate produces psychotic effects that limitits clinical utility (e.g. Besag F M, Expert Opin Drug Saf 3:1-8, 2004).

Gavestinel (GV-150,526) is another example of an antagonist at theglycine binding site for use as described herein. Other similarly usefulcompounds are described in DiFabrio et al., J Med Chem 40:841-50, 1997,which is hereby incorporated by reference. Other examples of glycinesite antagonists that are suitable for use in the pharmaceuticalcompositions and methods described herein are those referred to in thefollowing: U.S. Pat. No. 6,667,317 which was issued on Dec. 23, 2003;U.S. Pat. No. 6,080,743 which was issued Jun. 27, 2000; U.S. Pat. No.5,990,108, which was issued on Nov. 23, 1999; U.S. Pat. No. 5,942,540,which issued on Aug. 24, 1999; World Patent Application WO 99/34790which issued on Jul. 15, 1999; WO 98/47878, which was published on Oct.29, 1998; World Patent Application WO 98/42673, which was published onOct. 1, 1998; European Patent Application EP 966475A1, which waspublished on Dec. 29, 1991; World Patent Application 98/39327, which waspublished on Sep. 11, 1998; World Patent Application WO 98/04556, whichwas published on Feb. 5, 1998; World Patent Application WO 97/37652,which was published on Oct. 16, 1997; U.S. Pat. No. 5,837,705, which wasissued on Oct. 9, 1996; World Patent Application WO 97/20553, which waspublished on Jun. 12, 1997; U.S. Pat. No. 5,886,018, which was issued onMar. 23, 1999; U.S. Pat. No. 5,801,183, which was issued on Sep. 1,1998; World Patent Application WO 95/07887, which was issued on Mar. 23,1995; U.S. Pat. No. 5,686,461, which was issued on Nov. 11, 1997; U.S.Pat. No. 5,622,952, issued Apr. 22, 1997; U.S. Pat. No. 5,614,509, whichwas issued on Mar. 25, 1997; U.S. Pat. No. 5,510,367, which was issuedon Apr. 23, 1996; European Patent Application 517,347A1, which waspublished on Dec. 9, 1992; U.S. Pat. No. 5,260,324, which published onNov. 9, 1993. The foregoing patents and patent applications areincorporated herein by reference in their entireties.

GlyX-13 (Rapastinel) is a tetra-peptide(threonine-proline-proline-threonine) that functions as a mixedagonist/antagonist at the glycine site. NRX-1074 (apostimel) is anorally available molecule with similar properties to GlyX-13. NYX-2925((2S, 3R)-3-hydroxy-2-((R)-5-isobutyryl-1-oxo-2,5-diazaspiro[3.4]octan-2-yl)butanamide) is a small molecule designed based on effectof GlyX-3. AGN-241751 (Allergan) is an oral; available, small moleculeanalog of GlyX-13. CERC-301 (Rislenemdaz) is an oral active, selectiveNMDAR subunit 2B antagonist. AZD-6765 (Lanicemine) is a low-trappingNMDAR antagonist. S-ketamine (esketamine) is the S-isomer of racemicketamine R-ketamine is the R-isomer of racemic ketamine. AV-101(4-Chlorokynurenine (4-Cl Kyn) is an orally active small moleculeprodrug of 7-chlorokynurenic acid, which acts as an NMDAR glycine-siteantagonist.

Other examples of glycine site antagonists that can be used in thepharmaceutical composition and methods described herein areN-(6,7-dichloro-2,3-dioxo-1,2,3,4-tetrahydro-quinoxalin-5-yl)-N-(2-hydroxy-ethyl)-methanesulfonamideand6,7-dichloro-5-[3-methoxymethyl-5-(1-oxypyridin-3-yl)-[1,2,4]triazol-4-yl]-1,4-dihydro-quinoxa-line-2,3-dione.

Additional NMDAR antagonists for use herein are described in Schiene etal., U.S. Pat. Appl. No. US2001/0306674 A1, which is incorporated hereinby reference in its entirety, and include without being limited thereto,N-containing phosphonic acids, such as norvaline (AP5), D-norvaline(D-AP5), 4-(3-phosphono-propyl)-piperazine-2-carboxylic acid (CPP),D-(E)-4-(3-phosphonoprop-2-enyl)piperazine-2-carboxylic acid (D-CPPene),cis-4-(phosphonomethyl)-2-piperidine carboxylic acid (Selfotel, CGS19755), SDZ-220581, PD-134705, LY-274614 and WAY-126090; quinolinicacids, such as kynurenic acid, 7-chloro-kynurenic acid,7-chloro-thiokynurenic acid and 5,7-dichloro-kynurenic acid, prodrugsthereof, such as 4-chlorokynurenine and 3-hydroxy-kynurenine;4-aminotetrahydrochinolin-carboxylates, such as L-689,560;4-hydroxyquinolin-2(1H)-ones, such as L-701,324; quinoxalinediones, suchas licostinel (ACEA-1021) and CGP-68,730A;4,6-dichloro-indole-2-carboxylate derivatives such as MDL-105,519,gavestinel (GV-150,526) and GV-196,771A; tricyclic compounds, such asZD-9,379 and MRZ-2/576, (+)-HA-966, morphinan derivatives such asdextromethorphan and dextrophan; benzomorphans, such as BIII-277CL;other opioids, such as dextropropoxyphene, ketobemidone, dextromethadoneand D-morphine; amino-adamantanes, such as amantadine and memantine;amino-alkyl-cyclohexanes, such as MRZ-2/579; ifenprodil andifenprodile-like compounds such as eliprodil and PD-196,860;iminopyrimidines; or other NMDAR-antagonists such as nitroprusside,D-cycloserine, 1-aminocyclopropanecarboxylic acid, dizocilpine (MK 801)and its analogs, phencyclidine (PCP), ketamine((R,S)-2-(2-Chlorphenyl)-2-(methylamino)cyclohexan-1-on), (R)-ketamine,(S)-ketamine, remacemide and its des-glycinyl-metabolite FPL-12,495,AR-R-15,896, methadone, sulfazocine, AN19/AVex-144, AN2/AVex-73,Besonprodil, CGX-1007, EAB-318, Felbamate and NPS-1407.NMDAR-Antagonists are, for example, disclosed in “Analgesics,” edited byH. Buschmann, T Christoph, E. Friderichs, C. Maul, B. Sundermann, 2002,Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, in particular pages389-428. The respective parts of the description are hereby incorporatedby reference and form part of the present disclosure.

Along with identified NMDAR antagonists, additional effective compoundscan be identified using well-validated electrophysiological assays suchas modulation of NMDAR-mediated responses to NMDAR glutamate-siteagonists, or radioreceptor assays, such as modulation of binding to theNMDAR PCP-receptor channel binding site. Glycine site agonists andantagonists can also be distinguished based upon both electrophysiologyand receptor binding from compounds such as phencyclidine (PCP) orketamine that bind to the channel site. Partial agonists are defined ascompounds that have reduced efficacy for inducing conformational changein receptors (typically 40-80%) relative to full agonists. Mixedagonists/antagonists are compounds that may induce agonist effects atlow dose but antagonist effects at high dose.

The described methods relate to DCS provided in dosages intended toproduce blood and/or plasma concentrations above 25 microgram/mL. Itwill be understood D-cycloserine levels in blood and/or plasma may bedetermined using standard analytic techniques such as high-pressureliquid chromatography.

Plasma levels associated with anti-depressant effects of D-cycloserinecan be determined using rodent behavioral tests such as the forced swimtest (FST), which has previously been shown to sensitive to effects ofNMDAR glycine site antagonists such as 1-aminocyclopropanecarboxylateACPC (Trullas et al., Eur J Pharmacol. 1991; 203:379-385).

In general, locomotor hyperactivity is considered a rodent analog ofpsychotomimetic effect. A prior study did not find significant increasesin locomotor activity in mice when D-cycloserine was given at doses ofup to 160 mg/kg. Nevertheless, D-cycloserine potentiated the effects ofa low dose of the non-competitive NMDAR antagonist MK-801 (Carlsson M L,Engberg G, Carlsson A. Effects of D-cycloserine and (+)-HA-966 on thelocomotor stimulation induced by NMDARantagonists and clonidine inmonoamine-depleted mice. J Neural Transm Gen Sect. 1994; 95(3):223-233).

The second of the two active agents in the described pharmaceuticalcompositions is an antidepression agent.

In some embodiments, the antidepressant is a tetracyclic antidepressant(TeCA), selective serotonin reuptake inhibitor (SSRI), aserotonin/norephinephrine reuptake inhibitor (SNRI), an antipsychoticapproved for treatment of depression or a combination thereof. Otherantidepressants for use in the described compositions and methodsinclude monoamine oxidase inhibitors (MAOI), TCAs such as, but notlimited to imipramine, amitryptiline, desipramine, clomipramine, TeCAssuch as mianserin, mirtazapine, serotonin (SSRI) andserotonin/norephinephrine (SNRI) reuptake inhibitors, such asfluoxetine, fluvoxamine, paroxetine, citalopram, escitalopram,duloxetine, venlafaxine and others, as will be appreciated by theskilled artisan.

Current treatments for major depression consist primarily of olderantidepressants, such as monoamine oxidase inhibitors (MAOI) andtricyclic antidepressants (TCAs) (e.g. imipramine, amitryptiline,desipramine, clomipramine) that were first developed in the 1960's, andnewer agents such as tetracyclic antidepressants (TeCAs) (e.g.,mianserin, mirtazapine), serotonin (SSRI) and serotonin/norephinephrine(SNRI) reuptake inhibitors (e.g., fluoxetine, fluvoxamine, paroxetine,citalopram, escitalopram, duloxetine, venlafaxine, dapoxetine,indalpine, milnacipran, levomilnacipran). MAOIs and TCAs are considered“broader spectrum” agents than SSRIs/SNRIs that were developedsubsequently.

Other anti-depressant agents show differential mechanism of action.Bupropion is an antidepressant medication that works as anorepinephrine-dopamine reuptake inhibitor (NDRI) and is also approvedfor smoking cessation.

SNRIs may differ in relative specificity for serotonin (SERT) vs.norepinephrine (NET) transporters. For example, traditional SNRI agentssuch as venlafaxine, duloxetine and desvenlafaxine show substantiallygreater affinity for SERT versus NET transporters, whereas newer agentssuch as milnacipram and levomilnacipran show more balanced affinity forNET vs. SERT transporters. These compounds thus haveserotonin:norepinephrine reuptake ratios more similar to those of TCAsthan SSRIs or other SNRIs.

Vilazodone is considered an atypical antidepressant in that it functionsas both an SSRI and a partial agonist at 5HT1A receptors and has thusbeen termed a serotonin partial agonist and reuptake inhibitor (SPARI)(Schwartz et al., Vilazodone: A Brief Pharmacological and ClinicalReview of the Novel Serotonin Partial Agonist and Reuptake Inhibitor,Ther Adv Psychopharmacol. 1:81-87, 2011). The combination of serotoninreuptake inhibition and 5-HT1A agonist is believed to function as anantidepressant at lower levels of serotonin transporter occupancy thanotherwise (Kohler et al., J Psychopharmacogy, 30:13-22, 2016).

Vortioxetine is considered a multimodal antidepressant in that itfunctions as 1) a serotonin transport inhibitor, 2) a partial agonist at5-HT1A receptors, and 3) a partial antagonist of 5-HT1B, 5HT1D and 5-HT7receptors (Stahl S M, Modes and nodes explain the mechanism of action ofvortioxetine, a multimodal agent (MMA): enhancing serotonin release bycombining serotonin (5HT) transporter inhibition with actions at 5HTreceptors (5HT1A, 5HT1B, 5HT1D, 5HT7 receptors) CNS Spectrums (2015),20, 93-97)

Levopmilnacipran and milnacipran, while considered SNRIs, have a muchlower ratio of serotonin:norephinephrine ratio than previously marketedSNRI agents. Thus, whereas venlafaxine, duloxetine, and desvenlafaxineall have serotonin:noepinephrine ratios of 10:1 or greater,levomilnacipran has a ratio of only 1.2:1 and milnacipran has a ratio ofonly 1.6:1 (Sansone R A, Sansone L A Serotonin norepinephrine reuptakeinhibitors: a pharmacological comparison. Innov Clin Neurosci. 11 (3-4):37-42). Binding profiles of milnacipran and levomilnacipran are thusmore similar to TCAs than to other SNRIs.

Mirtazapine is a racemic mixture of S(+)mirtazapine (also calledS-mirtazapine) and R(−)mirtazapine (also called R-mirtazapine) thatfunctions as a noradrenergic and specific serotonergic antidepressant(NaSSA). Both the S(+)mirtazapine and R (−) mirtazapine enantiomers arepharmacologically active, but may have offsetting effects. Thus, forexample, in one study racemic mirtazapine produced biphasic effects in arodent nociception assay, whereas R(−)mirtazapine produced onlyanti-nociceptive effects and S(+)mirtazapine exerted pro-nociceptiveeffects (Freynhagen et al., Brain Res Bull 69:168-173, 2006).Differences in binding profile are also observed between the enantiomersthat confer differential effects on specific aspects of binding, thatmay confer advantages over the racemate for treatment of specificdisorders.

Approved dosing levels for the antidepressant agents described hereincan be determined from standard sources, such as packaged insertsapproved by the US Food and Drug Administration (FDA).

In some embodiments, the second therapeutic agent is provided at asubtherapeutic dose, if the second therapeutic agent were providedalone.

The provided compositions can be used in methods for treatingdepression, OCD, and anxiety disorders in a subject in need thereof, inwhich the subject is administer an oral dose of the describedcomposition as herein described.

In some embodiments of the methods of treating depression, the twoactive ingredients of the described composition are provided in a singlepharmaceutical composition. In other embodiments, the active agents areprovided separately.

In some embodiments, the subject has previously received treatment withan anti-depressant agent. In some embodiments, the said anti-depressantagent is ketamine. In some embodiments, the anti-depressant agent is ananti-NMDAR agent.

In some embodiments, the subject suffers from mania, or in someembodiments, the subject suffers from bipolar disorder.

In some embodiments, the invention provides a method for reducing theincidence or treating suicide or suicide ideation in a subject orpopulation in need thereof, the method comprising providing the subjectwith an oral dosage regimen as herein described. In such embodiments,the methods further include administering a second therapeutic agent forthe treatment of depression or for the reduction of the incidence ortreatment of suicide or suicide ideation in a subject or population inneed thereof.

In some embodiments, the regimen comprises administering a secondtherapeutic agent which is an anti-depressant, and said dosage is inaccordance with standard prescribing guidelines.

In some embodiments, the regimen comprises a second therapeutic agentwhich is a psychotropic medication.

In some embodiments, the pharmaceutical compositions can be administeredto the patient by any, or a combination, of several routes, for example,whereas D-cycloserine may be administered orally, the second therapeuticagent administered, as herein described may be administered by anyappropriate route, for example, such second therapeutic agent may beprovided as an oral, intravenous, trans-mucosal (e.g. nasal, vaginal,etc.), pulmonary, transdermal, ocular, buccal, sublingual,intraperitoneal, intrathecal, intramuscular, or long term depotpreparation.

In some embodiments, solid compositions for oral administration cancontain suitable carriers or excipients, such as corn starch, gelatin,lactose, acacia, sucrose, microcrystalline cellulose, kaolin, mannitol,dicalcium phosphate, calcium carbonate, sodium chloride, lipids, alginicacid, or ingredients for controlled slow release. Disintegrators thatcan be used include, without limitation, micro-crystalline cellulose,corn starch, sodium starch glycolate and alginic acid. Tablet bindersthat may be used include, without limitation, acacia, methylcellulose,sodium carboxymethylcellulose, polyvinylpyrrolidone (Povidone),hydroxypropyl methylcellulose, sucrose, starch, and ethylcellulose.

In some embodiments, liquid compositions for oral administrationprepared in water or other aqueous vehicles can include solutions,emulsions, syrups, and elixirs containing, together with the activecompound(s), wetting agents, sweeteners, coloring agents, and flavoringagents. Various liquid and powder compositions can be prepared byconventional methods for inhalation into the lungs of the patient to betreated.

In some embodiments, the second therapeutic agent may be formulated asan injectable composition, which may contain various carriers such asvegetable oils, dimethylacetamide, dimethylformamide, ethyl lactate,ethyl carbonate, isopropyl myristate, ethanol, polyols (glycerol,propylene glycol, liquid polyethylene glycol, and the like).

In some embodiments, the second therapeutic agent may be formulated asan intravenous injection, the compounds may be administered by the dripmethod, whereby a pharmaceutical composition containing the activecompound(s) and a physiologically acceptable excipient is infused.

Physiologically acceptable excipients may include, for example, 5%dextrose, to 0.9% saline, Ringer's solution or other suitableexcipients. For intramuscular preparations, a sterile composition of asuitable soluble salt form of the compound can be dissolved andadministered in a pharmaceutical excipient such as Water-for-Injection,0.9% saline, or 5% glucose solution, or depot forms of the compounds(e.g., decanoate, palmitate, undecylenic, enanthate) can be dissolved insesame oil. Alternatively, the pharmaceutical composition can beformulated as a chewing gum, lollipop, or the like.

While the dosage regimen and methods described herein represent anoptimum arrived at by administering the D-cycloserine orally, it will beappreciated by the skilled artisan that a lower dosage may beaccomplished with the same achieved plasma level by administering theD-cycloserine by a route that does not undergo first pass metabolism.According to this aspect, the dosage can be adjusted to be staggeredaccordingly, as presented for the oral dosage regimens described herein,with proportionately lower dosages, to accommodate a non-oraladministration route, and such alterations are to be considered to be anembodied regimen of this invention.

It will also be appreciated by the skilled artisan that a lower dosagemay be accomplished with the same achieved plasma level by administeringthe D-cycloserine in a formulation that undergoes reduced gastricdegradation, for example by applying an enteric coating.

In other embodiments, the formulations as herein described, inparticular with regard to oral formulations, are envisioned to compriseslow release tablet formulations. Such slow release tablet formulationsmay, for example, comprise commercially available formulationscontaining known anti-depressant medications, such as, for example,Effexor (venlafaxine) or Seroquel (quetiapine), both of which arealready available in extended length (XR) formulations, however theformulation may be modified to further incorporate D-cycloserine.

In other embodiments, the formulations as herein described, inparticular with regard to oral formulations, are envisioned to compriseboth short acting and extended release formulations. Extended releaseformulations have the advantage inter alia of minimizing the differencebetween peak and trough levels of drug, and thereby to increaseeffectiveness and/or reduce side effects of a medication.

Methods for the formulation of the described regimens herein are wellknown, and the skilled artisan will appreciate that it isstraightforward to prepare the oral dosage regimens as herein described.Applicants, for example, refer to Gibaldi's Drug Delivery Systems inPharmaceutical Care, Desai A & Lee M (eds), Bethesda, Md.: AmericanSociety of Health-System Pharmacists, 2007.

D-cycloserine has a relatively short half-life in man, and therefore ispresently used in BID dosing. In some embodiments of the invention BIDdosing is envisioned. According to this aspect, and in some embodiments,such consideration will nonetheless ensure that the daily dosagedescribed for the regimens defined herein are not exceeded.

In some embodiments of the invention, D-cycloserine is microencapsulatedto increase its circulating half-life. According to this aspect, and insome embodiments, the microencapsulated compound would then be combinedeither with an anti-depressant medication that is already administeredonce daily (e.g. sertraline, citalopram, aripiprazole) to insure thatcycloserine cannot be taken without accompanying antidepressant (whichwould increase risk of CNS side effects). Alternatively, the drug couldbe combined with an anti-depressant compound that is already typicallygiven in divided doses (e.g. venlafaxine, quetiapine) and the two drugscould then be microencapsulated in common to yield a once-dailyformulation with similar half-life between the two ingredients.Microencapsulation using standard approaches for (cf. Doshi D H, OralDrug Delivery Systems, in Gibaldi's Drug Delivery Systems inPharmaceutical Care, Desai A & Lee M (eds), Bethesda, Md.: AmericanSociety of Health-System Pharmacists, 2007. pp. 23-43) such as use ofcoating materials or matrix-based oral delivery systems. In oneapproach, for example, drugs are mixed with a gelling agent, such ashydroxypropylmethylcellulose or hydroxylpropylcellulose, which form ahydrophilic matrix (gel) upon contact with water that delays release ofthe compound. Release properties can be regulated by selection ofspecific gelling agents, as is known in the art (see, for example, U.S.Pat. No. 5,948,437; European patent EP20040765928, U.S. Pat. No.7,807,195).

Other compounds that can be used to control release include cellulose,ethylcellulose, gelatin, hypromellose, iron oxide and titanium oxide. Insome matrix systems, drug release is controlled mainly by diffusionthrough matrix pores and not by the erosion of the polymers. Drugdelivery can also be controlled by use of reservoir type systems inwhich release is controlled by osmotic gradient across the coatingmembrane. Capsules can be manufactured which contain granules withdifferent microencapsulation properties which can be blended to achievea composition that has a desired release rate.

In one embodiment of the invention, D-cycloserine is microencapsulatedalong with quetiapine or a pharmaceutically acceptable salt thereofusing a gelling agent such as hydroxypropyl methylcellulose, togetherwith one or more pharmaceutically acceptable excipients. In someembodiments, the sustained release formulation comprises a hydrophilicmatrix comprising a gelling agent, preferably hydroxypropylmethylcellulose, D-cycloserine, quetiapine and pharmaceuticallyacceptable salts thereof, together with one or more pharmaceuticallyacceptable excipients.

As described, the methods of treatment provided herein includeadministering to a subject at least two active ingredients for thetreatment of depression and other neuropsychiatric conditions.

NMDAR mediate a process termed long-term potentiation that may beexcessive in disorders such as depression, obsessive compulsivepersonality disorder (OCD), post-traumatic stress disorder (PTSD) orother stress-related disorders (SD) and anxiety disorders such asadjustment disorders with depressive, anxious or mixed features. NMDARexcess disorders may be identified by objective biological markers suchas reduced brain glutamate+glutamate (Glx) levels as detected usingmagnetic resonance spectroscopy (MRS) (e.g. Milak et al., MolPsychiatry. 2016; 21(3):320-7; Kantrowitz et al. Am J Psychiatry. 2016;173(12):1241-2).

Major depression is a clinical syndrome that includes a persistent sadmood or loss of interest in activities, which persists for at least twoweeks in the absence of treatment. Symptoms of major depression aretypically measured using rating scales such as the Hamilton DepressionRating Scale (HAM-D) or the Beck Depression Inventory (BDI). In additionto including symptoms relevant to depressed mood, the HAM-D alsocontains symptoms sensitive to psychosis, including items for guilt,depersonalization/derealization and paranoia.

Major depression may also be associated with symptoms of anxiety, whichmay be measured with rating scales such as the Hamilton Rating Scale forAnxiety (HAM-A). Depressive disorders are divided in major depression(MDD) and bipolar depression (BPD), which may be diagnosed usingcriteria set forth in the Diagnostic and Statistical Manual, 5thedition, published by the American Psychiatric Association (DSM-5),which provides as well additional description of mental disorders. Majordepression may also occur with and without melancholic features. Inaddition, depressive symptoms may occur in the context of anxietydisorders such as generalized anxiety disorder, dissociative disorders,personality disorders or adjustment disorders with depressed mood(DSM-5).

Other forms of depression include atypical depression, agitateddepression, depression with mixed emotional features, cyclothymia,dysthymia minor depression and adjustment disorder with depressed mood.Bipolar depression may be divided into Bipolar I and Bipolar II subtypesbased upon presence or absence of manic episodes. In bipolar disorder,depressive symptoms can occur in the context of either a depressiveepisode, or a mixed state in which symptoms of mania and depressionoccur simultaneously or in rapid sequence. Rapid cycling between maniaand depressive episodes may also occur in some individuals.

The first therapeutic agent in the described methods includes an NMDARantagonist, such as DCS provided at the net antagonist dose describedherein. The method further comprises administering a second therapeuticagent for the treatment of depression to said subject. In particularembodiments, the second therapeutic agent is administered in the samecomposition as the NMDAR antagonist. In other embodiments, it isadministered separately.

According to this aspect, the method is not limited in terms of thetiming of the administration of the second therapeutic agent, such thatthe methods of this invention contemplate a subject already treated witha second therapeutic agent, or a naive subject concomitantly treatedwith D-cycloserine and the second therapeutic agent, or in someembodiments, the subject initially treated with D-cycloserine is thenadministered a second therapeutic agent, and each of these scenariosrepresents an embodiment of this invention. Such second therapeuticagent will be any such agent as herein described, including atetracyclic antidepressant (TeCA), selective serotonin reuptakeinhibitor (SSRI), a serotonin/norephinephrine reuptake inhibitor (SNRI),an atypical antidepressant, an antipsychotic approved for treatment ofdepression or a combination thereof.

In some embodiments, in accordance with the methods/uses of thisinvention, the regimen comprises administering a second therapeuticagent at a dosage which is considered to be suboptimal for treatingdepression in said subject when treating said subject with said secondtherapeutic agent alone.

In some embodiments, the methods of treatment are directed to reducingthe incidence or treating suicide or suicide ideation in a subject orpopulation. In some embodiments, the medicaments in accordance with thedescribed uses of this invention further comprises a second therapeuticagent for reducing the incidence or treating suicide or suicide ideationin a subject or population.

According to this aspect, the method is not limited in terms of thetiming of the administration of the second therapeutic agent, such thatthe methods of this invention contemplate a subject or populationalready treated with a second therapeutic agent, or a naive subject orpopulation concomitantly treated with D-cycloserine and the secondtherapeutic agent, or in some embodiments, the subject or population isinitially treated with D-cycloserine and then administered a secondtherapeutic agent, and each of these scenarios represents an embodimentof this invention. Such second therapeutic agent will be any such agentas herein described, including a tetracyclic antidepressant (TeCA),selective serotonin reuptake inhibitor (SSRI), aserotonin/norephinephrine reuptake inhibitor (SNRI), an atypicalantidepressant or an antipsychotic approved for reducing the incidenceor treating suicide or suicide ideation in a subject or population or acombination thereof.

In some embodiments, in accordance with the methods of this invention,the regimen comprises administering a second therapeutic agent at adosage which is considered to be suboptimal for reducing the incidenceor treating suicide or suicide ideation in a subject or population whentreating said subject with said second therapeutic agent alone.

As described in Textbook of INTERNAL MEDICINE, Kelley, et al. (eds.),Part X: Neurology, Chapter 469: Major Psychiatric Disorders, (J.Lippincott Co., Philadelphia), pp. 2198-2199 (1992), depression canoccur throughout life and is at least twice as common in women as inmen. Patients often present without the subjective sense of beingdepressed but complaining of somatic symptoms of depression, mostcommonly fatigue, sleep disturbances, or impotence. Patients maydescribe feeling sad, blue, low, irritable, or anxious, as well as beingdepressed. Diagnosis of major depression is based either on a distinctchange of mood that is prominent, generally persists throughout the day,and occurs each day for at least 2 weeks or on markedly diminishedinterest or pleasure in most activities over a similar period. Thediagnosis requires that at least four of the following symptoms bepresent nearly every day for a period of 2 weeks: significant weightloss (or weight gain in some younger patients), prominent sleepdisturbance, agitation or retardation with slow speech, fatigue,feelings of worthlessness and guilt, slowed thinking, and hopelessness.

Depression can likewise be associated with the symptoms of disease(e.g., systemic lupus erythematosus) or as a side effect of thetreatment of disease (e.g., with antihypertensive therapy). One form ofdepression, postpartum depression, has been commonly found in womenduring the period following childbirth.

The methods and materials of this invention are therefore suitable fortreatment of depression or symptoms of depression associated with otherdiseases, as herein described.

In some embodiments, according to this aspect, the subject haspreviously been administered or is concurrently administered a secondtherapeutic agent for the treatment of depression.

In some embodiments, according to this aspect, the second therapeuticagent comprises any such agent as herein described, for example, atetracyclic antidepressant (TeCA), selective serotonin reuptakeinhibitor (SSRI), a serotonin/norephinephrine reuptake inhibitor (SNRI),a or atypical antidepressant with reduced serotonergic effects, anantipsychotic approved for use in treatment of depression or acombination thereof.

In some embodiments, according to this aspect, the second therapeuticagent is administered at a dosage, which is considered to be suboptimalfor treating depression in said subject when treating said subject withsaid second therapeutic agent alone.

In some embodiments, the invention further provides for the use ofD-cycloserine in the preparation of a medicament formulated for oraladministration at a dosage of >500 to <1000 mg/day for the treatment ofdepression in a subject in need thereof, wherein the dose is formulatedto produce sustained plasma levels of between 25-35 microgram/mL.

In some embodiments according to the aspect, the invention furtherprovides for the use of D-cycloserine in the preparation of a medicamentformulated for oral administration at a dosage of 10-25 mg/kg/day forthe treatment of depression in a subject in need thereof, wherein thedose is formulated to produce sustained plasma levels of between 25-35microgram/mL. It will be appreciated that the foregoing DCS dosages areapplicable to all of the compositions and methods described herein.

In some embodiments, plasma levels produced by D-cycloserineadministration are sustained from 30 minutes to 2 hours followingadministration.

In some embodiments according to the aspect, plasma levels produced byD-cycloserine administration are sustained from 30 minutes to 12 hoursfollowing administration.

A subject undergoing treatment with the methods of the invention canexperience significant improvements in depression. Relative to subjectstreated with alternative treatments for depression, subjects treatedaccording to the methods of the invention will experience, in someembodiments, greater improvement, or more long-lasting improvement, asmeasured by any clinically recognized assessment method for depression(e.g., the 21-item Hamilton Depression Rating Scale). It should be notedthat not every subject will benefit from the methods of the invention,just as other pharmaceutical agents do not typically benefit everypatient.

The following examples are provided to illustrate certain particularfeatures and/or embodiments. These examples should not be construed tolimit the disclosure to the particular features or embodimentsdescribed.

EXAMPLES Example 1: Demonstration of Locomotor Hyperactivity Effects ofD-Cycloserine in Rodents and Effects of Anti-Depressant Agents

For this study, psychomotor effects of D-cycloserine were assessed usingthe rodent open field test following D-cycloserine administration, inthe presence or absence of antidepressant agents.

All testing was performed at PsychoGenics Inc, 765 Old Saw Mill RiverRoad, Tarrytown, N.Y. 10591, USA

Male C57BL/6J mice (8 weeks old) from Jackson Laboratories (Bar Harbor,Me.) were used. Upon receipt, mice were assigned unique identificationnumbers (tail marked) and were group housed in OPTImice cages. Allanimals were acclimated to the colony room for 1 week prior to testing.During the period of acclimation, animals were examined on a regularbasis, handled, and weighed to assure adequate health and suitability.Animals were maintained on a 12/12 light/dark cycle. The roomtemperature was maintained between 20 and 23° C. with a relativehumidity maintained between 30% and 70%. Chow and water were provided adlibitum for the duration of the study. All testing was performed duringthe animal's light cycle phase.

Test compounds included

-   -   D-cycloserine (300 mg/kg) was dissolved in PTS vehicle (5%        PEG200: 5% Tween80: 90% NaCl) and administered IP at a dose        volume of 10 mL/kg in the open field test.    -   Bupropion (10 mg/kg) was dissolved in saline and administered IP        at a dose volume of 10 mL/kg 30 minutes prior to D-cycloserine        in the open field test.    -   Desipramine (10 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to        D-cycloserine in the open field test    -   Sertraline (20 mg/kg) was dissolved in sterile water and        administered IP at a dose volume of 10 mL/kg 30 minutes prior to        D-cycloserine in the open field test    -   Venlafaxine (40 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to        D-cycloserine in the open field test    -   Duloxetine (40 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to        D-cycloserine in the open field test    -   Fluoxetine (10 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to        D-cycloserine in the open field test    -   Imipramine (10 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to        D-cycloserine in the open field test    -   Citalopram (10 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to        D-cycloserine in the open field test    -   Levomilnacipran (40 mg/kg) was dissolved in sterile water and        administered IP at a dose volume of mL/kg 30 minutes prior to        D-cycloserine in the open field test    -   Milnacipran (40 mg/kg) was dissolved in sterile water and        administered IP at a dose volume of mL/kg 30 minutes prior to        D-cycloserine in the open field test    -   Vilazodone (1 mg/kg) was dissolved in PTS vehicle (5% PEG200: 5%        Tween80: 90% NaCl) and administered IP at a dose volume of 10        mL/kg 30 minutes prior to D-cycloserine in the open field test    -   Vortioxetine (10 mg/kg) was dissolved in PTS vehicle (5% PEG200:        5% Tween80: 90% NaCl) and administered IP at a dose volume of 10        mL/kg 30 minutes prior to D-cycloserine in the open field test

The open field (OF) test was performed using Plexiglas square chambers(27.3×27.3×20.3 cm; Med Associates Inc., St Albans, Vt.) surrounded byinfrared photobeams (16×16×16) to measure horizontal and verticalactivities. Mice were brought to the activity experimental room for atleast 1 hr acclimation to the experimental room conditions prior totesting. Animals were administered with vehicle, or test compound andplaced in the OF. For assessment of D-cycloserine effects, mice wereinjected with DCS prior to entry into the test chamber, and activity wasmonitored for 60 min. Alternately, vehicle or D-cycloserine wasadministered 30-min prior to challenge with amphetamine (4 mg/kg) orphencyclidine (5 mg/kg), and activity was summed for 60 min followingvehicle or D-cycloserine administration. For other conditions, animalswere treated with vehicle or antidepressant agents, following whichbaseline activity was recorded for 30 minutes. Mice then received DCSinjections and were placed back into OF chambers for a 60 minutesession. At the end of each OF test session the OF chambers werethoroughly cleaned.

Data were analyzed by analysis of variance (ANOVA) followed by post-hoccomparisons using Fishers's LSD test as appropriate. An effect wasconsidered significant if p<0.05.

TABLE 1 Summary of Locomotor activity data showing number of animals(N), Mean distance travelled over 30 min (Mean), Standard deviation andstatistical comparisons for animals treated with Vehicle orD-cycloserine Std. Condition N Mean Deviation p vs. Vehicle Vehicle 10.04881.4 1165.3 DCS, 30 mg/kg 10.0 4432.1 1712.9 0.5 DCS, 300 mg/kg 10.07588.5 1456.2 <0.001 DCS, 1000 mg/kg 9.0 9049.8 1862.9 <0.001

Results: Dose-response was assessed for 30 min after administration ofvehicle or D-cycloserine at doses between 30 and 1000 mg/kg. Across allconditions, there was a highly significant effect (F=19.0, df=3.35,p<0.001). Locomotor activity was not significantly affected byD-cycloserine administered at a dose of 30 mg/kg (p=0.5), but wassignificantly increased by both 300 mg/kg (p<0.001) and 1000 mg/kg(p<0.001) doses of D-cycloserine (Table 1).

When conditions were separated according to drug type including NDRIs(buproprion), tricyclic anti-depressants (desipramine, imipramine).SSRIs/SNRIs associated with high serotonergic transport (SERT)inhibition activity (sertraline, venlafaxine, duloxetine, fluoxetine,citalopram) vs. newer agents associated with low serotonergic transportinhibition activity relative to other targets such as norepinephrinetransporters or 5-HT1A receptors (levomilnacipran, milnacipran,vilazodone, vortioxetine), unexpected differences among the drug classeswere observed (Table 2).

Across all medication types, there was a highly significant main effectof treatment type (F=12.5, df=3.116, p<0.001). Among antidepressants,highest levels of activity (greatest psychotomimetic effect) wereobserved with DCS combined with either traditional SSRIs/SNRIs orbupropion. By contrast, locomotor activity was significantly lower withDCS combined with TCAs (p<0.001) or newer SNRIs/atypical antidepressants(p<0.001) relative to traditional SSRIs/SNRIs. In addition, locomotoractivity was significantly lower in combination withmilnacipran/levomilnacipran (p=0.003), vilazodone (p=0.007) andvortioxetine (p=0.014) than with traditional SSRIs/SNRIs, suggestingsignificant individual utility of these agents in combination withD-cycloserine.

TABLE 2 Summary of locomotor activity data showing number of animals(N), Mean distance travelled over 60 min (Mean), Standard deviation andstatistical comparisons for animals treated with Vehicle orD-cycloserine (DCS) Std. p val vs. Condition (DCS 300 mg/kg + Devia-traditional indicated agents) N Mean tion SSRIs/SNRIs TraditionalSSRIs/SNRIs 50 11307.45 8447.01 — bupropion 10 11526.89 6781.38 p = 0.9 TCAs 20 2210.92 2216.64 p < 0.001 milnacipran/levomilnacipran 20 5996.444680.51 p = 0.003 vilazodone 10 5118.55 3008.78 p = 0.007 vortioxetine10 5682.96 6096.93 p = 0.014

This is the first study of which we are aware to show that D-cycloserineon its own produces locomotor hyperactivity in rodents, suggestive of aclinical psychotomimetic effect. Taken together with a prior studyshowing no significant effect of D-cycloserine administered at a dose of160 mg/kg (Carlsson et al., J Neural Transm 95:223-233, 1994), thesefindings demonstrate that psychotomimetic effects are observedpreferentially at plasma levels exceeding 25 micrograms/mL (see Example3).

This is also the first study of which we are aware to show thatantidepressants show differential effects on locomotor hyperactivity inthe presence of D-cycloserine, with preferential effect noted for agentssuch as TCAs or the newer antidepressants vilazodone, vortioxetine,milnacipran and levomilnacipran, relative to traditional SSRI/SNRIs orbupropion, a dopamine-norepinephrine reuptake inhibitor.

Newer SNRIs and atypical antidepressants differ from traditionalmedications in that they have higher specificity for targets other thanthe serotonin transporter, and thus are relatively more similar to TCAs.These findings show unexpectedly that newer SNRIs/atypicalantipsychotics have preferential beneficial activities in combinationwith a D-cycloserine-dose associated with plasma levels >25microgram/mL, and thus show unexpected utility of combinations involvinghigh dose D-cycloserine and newer anti-depressant agents.

Example 2: Effects of NMDAR Antagonists Alone and Combined withAntidepressants and Antidepressants in the Rodent Forced Swim Test

For this study, anti-depressant effects of NMDAR antagonists wereassessed using the rodent forced swim tests. NMDAR antagonists werestudied alone and in combination with specific antidepression agents.

All testing was performed at PsychoGenics Inc, 765 Old Saw Mill RiverRoad, Tarrytown, N.Y. 10591, USA

Male BalbC/J mice (8 weeks old) from Jackson Laboratories (Bar Harbor,Me.) were used. Upon receipt, mice were assigned unique identificationnumbers (tail marked) and were group housed in OPTImice cages. Allanimals were acclimated to the colony room for 1 week prior to testing.During the period of acclimation, animals were examined on a regularbasis, handled, and weighed to assure adequate health and suitability.Animals were maintained on a 12/12 light/dark cycle. The roomtemperature was maintained between 20 and 23° C. with a relativehumidity maintained between 30% and 70%. Chow and water were provided adlibitum for the duration of the study. All testing was performed duringthe animal's light cycle phase.

Mice were acclimated to the test room at least 1 hour prior tocommencing the test. The forced swimming test consisted of one 6-minutesession of forced swimming in individual opaque cylinders (15 cm tall×10cm wide, 1000 ml beakers) containing fresh tap water at a temperature of23±2° C. and a depth of 12 cm (approximately 800 ml) for each testanimal. The time the animal spent immobile was recorded over the 6 mintrial. Every 1 min the cumulative immobility time was recorded from thestart of the session and noted on the study data record sheet Immobilitywas defined as the postural position of floating in the water. Theanimals were generally observed with the back slightly hunched and thehead above water with no movements or with small stabilizing movementsof the limbs. After the swim test, each animal was placed in apre-heated cage with a heating pad and allowed to dry.

The main variable used to represent immobility in this test was thetotal time immobile during the 6-min test period. Statistics wereperformed by analysis of variance (ANOVA) with Dunnett post-hoc testingvs. the control condition or by t-test as appropriate.

NRIs, SSRIs, SNRIs, TeCAs, atypical and multimodal antidepressants areall indicated for the treatment of depression. In this example,potential for additive effect was evaluated across a range ofanti-depressants. The forced swim test was used as described inExample 1. Compounds tested were as follows:

-   -   D-cycloserine (DCS 300 mg/kg) was dissolved in PTS vehicle and        administered IP at a dose volume of 10 ml/kg 30 min prior to        test.    -   Bupropion (10 mg/kg) was dissolved in saline and administered IP        at a dose volume of 10 mL/kg 30 minutes prior to test.    -   Desipramine (10 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to test.    -   Imipramine (10 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to test.    -   Sertraline (20 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to test.    -   Venlafaxine (40 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to test.    -   Duloxetine (40 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to test.    -   Fluoxetine (10 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to test.    -   Citalopram (10 mg/kg) was dissolved in saline and administered        IP at a dose volume of 10 mL/kg 30 minutes prior to test.    -   Levomilnacipran (40 mg/kg) was dissolved in sterile water and        administered IP at a dose volume of mL/kg 30 minutes prior to        test    -   Milnacipran (40 mg/kg) was dissolved in sterile water and        administered IP at a dose volume of mL/kg 30 minutes prior to        test    -   Vilazodone (1 mg/kg) was dissolved in PTS vehicle and        administered IP at a dose volume of 10 mL/kg 30 minutes prior to        test.    -   Vortioxetine (10 mg/kg) was dissolved in PTS vehicle and        administered IP at a dose volume of 10 mL/kg 30 minutes prior to        test.    -   Mirtazapine (5 mg/kg) were dissolved in PTS vehicle and        administered IP at a dose volume of 10 mL/kg 30 minutes prior to        test.

Results are shown in FIG. 2. Effects of DCS 300 mg/kg were highlysignificant across all agents tested. Particular beneficial effects wereobserved for bupropion, sertraline, and duloxetine where effects ofcombined antidepressant and DCS 300 mg/kg were significantly larger thanwith either agent alone.

Results for D-cycloserine (DCS) alone are shown in FIG. 1. DCS had nosignificant effect in the forced swim test assay at a dose of 30 mg/kg.By contrast, DCS had a statistically significant (p<0.001) reductionwhen administered at doses of 100 mg/kg or above.

Results for combined DCS and antidepression agents are shown in FIG. 2.In all cases, effects of DCS were maintained in the presence ofspecified agents, as reflected in the difference between combinedtreatment and the control, no DCS condition. Specific additionbeneficial effects were observed in combination with bupropion, TCAs,sertraline, venlafaxine, duloxetine, fluoxetine, vortioxetine andmirtazapine. Combinations with bupropion, sertraline, and duloxetineproduced effects greater than DCS alone.

Example 3: Pharmacokinetics of D-Cycloserine in Rodents

For this study, the pharmacokinetics of D-cycloserine in rodents wereassessed. This study tests the hypothesis that antidepressant effects ofDCS presented in the above examples are observed specifically attreatment levels that produce sustained blood DCS levels of >25microgram/mL.

For this study, male C57BL/6J mice (8 weeks old) from JacksonLaboratories (Bar Harbor, Me.) were used. D-cycloserine (30, 100, 300,500 and 1000 mg/kg) was dissolved in PTS vehicle (5% PEG200: 5% Tween80:90% NaCl) and administered IP at a dose volume of 10 mL/kg.

For each treatment group a total of 12 mice were dosed: 4 mice werecollected at 30, 60 and 120 min. Mean plasma level was computed over the30-60 min time period.

Analysis of DCS in plasma was performed utilizing an UPLC/MS/MS systemconsisted of an Acquity UPLC chromatographic system and a QuattroPremier XE triple quad mass spectrometer, both from Waters. Isolation ofDCS was achieved using a 5 minute (total run time) HILIC methodologywhich provided an LLOQ of 5 ng/mL.

Results of the experiment are shown in Table 1. As shown, peripheralD-cycloserine administration was associated with a dose-dependentincrease in plasma D-cycloserine over the 30-60 min time period(p<0.0001). Plasma levels associated with 30 mg/kg DCS treatment wereassociated with a mean plasma level below 25 microgram/mL. Plasma levelsassociated with the 100 mg/kg dose or higher were all significantlydifferent from 25 μg/mL (p<0.001). The maximum tolerated dose was500-1000 mg/kg, suggesting a maximum tolerated blood level ofapproximately 500 ug/mL.

These findings provide a demonstration that blood D-cycloserine levelsassociated with an antidepression effect in rodents (300 mg/kg) produceplasma levels in excess of 25 microgram/mL.

TABLE 3 Mean plasma levels (microgram/mL) over 30-60 min followingadministration of D-cycloserine to rodents p-value vs. Dose (mg/kg) meanStd dev Std err 25 μg/mL 30 24.89 4.86 2.43 0.966 100 74.92 7.26 3.63<0.001 300 251.48 28.67 14.34 <0.001 500 375.44 25.20 12.60 <0.000 1000510.73 71.56 35.78 <0.001

Example 4: Antidepressant and Anti-Anxiety Effects of CombinedDCS+Anti-Depressants

As noted in Example 1, significant beneficial effects were observed withthe combination of mirtazapine+D-cycloserine. Mirtazapine is a racemiccompound consisting of 2 stereoisomers: R-ketamine and S-ketamine. Here,we evaluated the relative effects of the isomers on forced swim testactivity.

Test compounds included DCS formulated as described above, andMirtazapine, R-Mirtazapine and S-Mirtazapine (5 mg/kg) which weredissolved in PTS vehicle and administered IP at a dose volume of 10mL/kg 30 minutes prior to test.

Results are shown in Table 4: As shown, highly significant beneficialeffects were observed with all combinations as shown by highlysignificant p-values vs. control. In all combinations, DCS also addedsignificantly to anti-depressant effects of mirtazapine or its isomersas shown by significant p values for DCS vs. no DCS. Finally,significantly greater beneficial improvement was noted with combinedDCS+R-mirtazapine vs. DCS+S-mirtazapine as shown by the significantvalues between the two compounds. Although R-mirtazapine and racemicmirtazapine did not differ statistically, reduction in immobility wasnumerically greater in the presence of R- vs. racemic mirtazapine inboth the absence and presence of DCS.

These studies demonstrate unanticipated preferential effects ofR-mirtazapine+DCS vs. other combinations.

TABLE 4 Immobility time (sec) in the rodent forced swim test (FST) underindicated conditions. p-value: p-value DCS vs. p-value: R vs. ConditionN Mean Std vs. ctl no DCS S-mirtazapine Ctl 50 127.50 42.97 — — DCS 300mg/kg 50 42.08 47.60 p < 0.001 p < 0.001 Mirtzapine 5 mg/kg 10 92.3066.59 p = 0.03 — Mirtzapine + DCS 10 31.20 26.47 p < 0.001 p < 0.001S-mirtazipine 5 mg/kg 10 117.60 43.44 p < 0.001 — S-mirtazipine + DCS 1072.50 48.04 p < 0.001 p < 0.001 R-mirtazipine 5 mg/kg 110 68.40 42.64 p< 0.001 — p = 0.016 R-mirtazipine + DCS 110 27.60 32.80 p < 0.001 p <0.001 p = 0.028from the cages and the number of unburied marbles was counted. A marblewas considered buried if it was covered at least two thirds withbedding.

The following compounds were used. All compounds were administered at adose volume of 10 ml/kg:

-   -   D-cycloserine (Sigma, DSC; 30 and 300 mg/kg) was dissolved in 5%        PEG 200: 5% Tween 80: 90% saline (PTS) and administered IP 30        min prior to test at a dose volume of 10 ml/kg.    -   Mirtazapine (Sigma, 5.5 mg/kg) was dissolved in 5% PEG 200: 5%        Tween 80: 90% saline (PTS) and administered IP 30 min prior to        test at a dose volume of 10 ml/kg    -   Paroxetine (Sigma, 5 mg/kg) was used as the positive reference        in the marble burying test. This compound was dissolved in 20%        cyclodextrin and administered IP 30 min prior to test at a dose        volume of 10 ml/kg.    -   Combination DSC (300 mg/kg)+Mirtazapine (5.5 mg) was        administered IP as a cocktail in a single injection 30 minutes        prior to test at a dose volume of 10 ml/kg. 10 mice were tested        in each of the following test groups:        -   Vehicle (5% PEG200; 5% Tween80; 90% Saline)        -   Paroxetine (5 mg/kg)        -   Mirtazapine (5.5 mg/kg)        -   D-cycloserine (30 mg/kg)        -   D-cycloserine (300 mg/kg)        -   D-cycloserine (300 mg/kg)+(Mirtazapine 5.5 mg/kg)

Results of the study are shown in FIG. 3. One-Way ANOVA found asignificant treatment effect. Post-hoc comparisons demonstrated thatParoxetine (5 mg/kg) as well as Mirtazapine (5.5 mg/kg) significantlyreduced the number of marbles buried compared to vehicle. Treatment ofanimals with either dose of D-Cycloserine (30 mg/kg, and 300 mg/kg) didnot affect this measure. The combination of D-cycloserine (300 mg/kg)and Mirtazapine (5.5 mg/kg) significantly reduced the number of marblesburied compared to vehicle and Mirtazapine (5.5 mg/kg) alone.

These findings demonstrate significant unexpected synergy between DCS,administered at an NMDAR antagonist, 300 mg/kg dose, and theanti-depressant mirtazapine on behaviors related to anxiety, OCD andPTSD, and support combined NMDAR antagonist and anti-depressanttreatment of PTSD.

Example 6: Differential Effects of R- and S-Isomers of Mirtazapine onMarble Burying

Mirtazapine is a racemic mix of separate R(−) and S(+) isomers. Afollow-up study evaluated the relative effects of the two isomersindependently. Methods are the same as for Example 3. Test compounds areas follows:

-   -   5% PEG 200: 5% Tween 80: 90% saline (PTS) was administered IP 30        min prior to test at a dose volume of 10 ml/kg    -   Paroxetine (5 mg/kg) was dissolved in saline and was        administered IP 30 min prior to test at a dose volume of 10        ml/kg    -   D-cycloserine (Sigma, DSC; 300 mg/kg) was dissolved in 5% PEG        200: 5% Tween 80: 90% saline (PTS) and administered IP 30 min        prior to test at a dose volume of 10 ml/kg.    -   Mirtazapine (Sigma,1,2.5, 5.0, and 10 mg/kg) was dissolved in 5%        PEG 200: 5% Tween 80: 90% saline (PTS) and administered IP 30        min prior to test at a dose volume of 10 ml/kg    -   S-Mirtazapine (TRC, 1,2.5, 5.0, and 10 mg/kg) was dissolved in        5% PEG 200: 5% Tween 80: 90% saline (PTS) and administered IP 30        min prior to test at a dose volume of 10 ml/kg    -   R-Mirtazapine (TRC, 1,2.5, 5.0, and 10 mg/kg) was dissolved in        5% PEG 200: 5% Tween 80: 90% saline (PTS) and administered IP 30        min prior to test at a dose volume of 10 ml/kg

The effects of paroxetine, mirtazapine, S-mirtazapine, R-mirtazapine andD-cycloserine on marble-burying behavior are presented in FIG. 4.One-Way ANOVA found a significant treatment effect. Post-hoc comparisonsdemonstrated that paroxetine (5 mg/kg), mirtazapine (1, 2.5, 5, and 10mg/kg), S-mirtazapine (1, 2.5, 5, 10 mg/kg), as well as R-mirtazapine(10 mg/kg) significantly reduced the number of marbles buried comparedto vehicle. R-mirtazapine (1, 2.5, and 5 mg/kg), did not affect thismeasure. Effects of S-mirtazapine were significantly more robust thanracemic mirtazapine, whereas effects of R-mirtazapine were less robust(FIG. 2), showing superiority of S-isomer over the racemate fortreatment of anxiety-related conditions including OCD and PTSD.

Across the 3 mirtazapine formulations (racemate, R-, S-) there was ahighly significant main effect of DCS treatment (F=27.2, df=1.54,p<0.001) supporting prior findings. Mirtazapine (2.5 mg/kg)+DSC (300mg/kg) combination significantly reduced number of marbles buriedcompared to mirtazapine (2.5 mg/kg) alone (p<0.01). Additionally, thecombination of R-mirtazapine (2.5 mg/kg)+DSC (300 mg/kg) significantlyreduced number of marbles buried compared to combination ofR-mirtazapine (2.5 mg/kg)+PTS vehicle (p<0.01). In the presence ofS-mirtazapine, floor level effects were observed in both the absence andpresence of DCS, so no comparisons could be performed.

In view of the many possible embodiments to which the principles of thedisclosed invention may be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. We thereforeclaim as our invention all that comes within the scope and spirit ofthese claims.

I claim:
 1. A method for treatment of a NMDA receptor-responsiveneuropsychiatric disorder selected from the group consisting ofdepression, obsessive compulsive disorder, and anxiety disorders, themethod comprising administering to a subject in need thereof acomposition comprising: a first agent consisting of a NMDA receptorantagonist; and an anti-depressant selected from the group consisting oflevomilnacipran, milnacipran, vilazadone, vortioxetine, S-mirtazapineand R-mirtazapine, thereby treating the NMDA receptor-responsiveneuropsychiatric disorder.
 2. The method of claim 1 wherein, the firstagent is D-cycloserine provided at a net antagonistic dose.
 3. Themethod of claim 2, wherein the D-cycloserine is administered at a doseof ≥500 mg/day to ≤1000 mg/day and is formulated to produce an averageplasma level in the subject of greater than 25 μg/mL.
 4. The method ofclaim 2, wherein the D-cycloserine is administered at a dose of 7.5-12.5mg/kg/day.
 5. The method of claim 1, wherein the first agent is selectedfrom the group consisting of ketamine, S-Ketamine, R-ketamine, GlyX-13,NRX-1074, NYX-2925, AGN-241751, CERC-301, AZD6765, AV101 and Gavestinel.6. The method of claim 1, wherein the NMDA receptorantagonist-responsive neuropsychiatric disorder is depression.
 7. Themethod of claim 6, wherein the depression is major depression, majordepressive disorder, atypical, agitated, melancholic depression ordysthymic disorder.
 8. The method of claim 1, wherein the depression isbipolar disorder.
 9. The method of claim 8, wherein the bipolar disorderis bipolar type I or bipolar type 2 depressive disorder.
 10. The methodof claim 8, wherein the bipolar disorder is depressive or mixed episodesassociated with bipolar depression.
 11. The method of claim 1, whereinthe composition reduces symptoms of depression, reduces suicideincidence or treats suicide ideation in the subject.
 12. The method ofclaim 1, wherein the NMDAR antagonist-responsive neuropsychiatricdisorder is associated with suicidality.
 14. The method of claim 1,wherein the first and second agents are provided in a singlepharmaceutical composition.
 15. The method of claim 1, wherein thecomposition is formulated for sustained release delivery.
 16. Acomposition comprising: a first agent consisting of a NMDA receptorantagonist; and a second agent consisting of an antidepressant selectedfrom the group consisting of levomilnacipran, milnacipran, vilazadone,vortioxetine, S-mirtazapine and R-mirtazapine.
 17. The composition ofclaim 16, wherein first agent is D-cycloserine provided at a netantagonistic dose.
 18. The composition of claim 17, wherein theD-cycloserine is formulated to provide a dose of ≥500 mg/day to ≤1000mg/day and to produce an average plasma level in a subject of greaterthan 25 μg/mL.
 19. The composition of claim 17 or claim 18, wherein theD-cycloserine is formulated to provide a dose of 7.5-12.5 mg/kg/day. 20.The composition of claim 16, wherein the first agent is selected fromthe group consisting of ketamine, GlyX-13, AGN-241751 and Gavestinel.